1. Field of the Invention
The present invention relates to an improvement in an ophthalmic instrument equipped with an alignment function which automatically aligns the main body of the instrument with a subject eye to be tested.
2. Description of the Related Art
A conventional ophthalmic instrument with an alignment function, such as a non-contact type tonometer, is provided with a stopper which limits the range in which the main body of the instrument moves in the back-and-forth direction, for the purpose of avoiding a collision between a testee and the main body of the instrument. This stopper can adjust its position as needed and is constructed so that it can change the moving range of the main body of the instrument. And a tester adjusts the minimum distance between the main body of the instrument and a testee by adjusting the position of this stopper.
Incidentally, it has also been proposed that during position adjustment of the stopper, the drive of a measuring portion by an automatic alignment function is limited (Japanese Laid-Open Patent Publication No. HEI 8-266475). That is, if a knob for moving the stopper is pushed, the stopper is moved and the movable range of the main body of the instrument is changed. While this stopper moving knob has been pushed, the drive of a drive portion for driving the measuring portion is inhibited. With this, it can be avoided that unnecessary measurement is performed during the position adjustment of the stopper.
However, the above-mentioned prior art can avoid only unnecessary measurement during the position adjustment of the stopper, but it cannot avoid unnecessary measurement immediately after the tester releases hold of the stopper moving knob. That is, at the time the tester has released hold of the stopper moving knob, there are cases where accidentally the main body of the instrument is at a position which satisfies alignment start conditions. And in such cases, there is a fear that the conventional ophthalmic instrument will start a measurement which the tester does not intend.